The invention generally relates to vascular catheters suitable for maintaining the patency of a blood vessel after a vascular procedure therein, such as angioplasty. In particular, the present invention relates to angioplasty apparatus facilitating rapid exchanges and a method for making rapid exchanges of angioplasty devices.
In typical percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and is advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guide wire and a dilatation catheter having an inflatable balloon on the distal end thereof are introduced through the guiding catheter with the guide wire slidably disposed within an inner lumen of the dilatation catheter. The guide wire is first advanced out of the distal end of the guiding catheter and is then maneuvered into the patient's coronary vasculature containing the lesion to be dilated, and is then advanced beyond the lesion. Thereafter, the dilatation catheter is advanced over the guide wire until the dilatation balloon is located across the lesion. Once in position across the lesion, the balloon of the dilitation catheter is filled with radiopaque liquid at relatively high pressures (e.g., greater than about four atmospheres) and is inflated to a predetermined size (preferably the same as the inner diameter of the artery at that location) to radially compress the atherosclerotic plaque ofthe lesion against the inside of the artery wall to thereby dilate the lumen of the artery. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
A common problem that sometimes occurs after an angioplasty procedure is the development of restenosis at or near the site of the original stenosis in the body lumen which requires a second angioplasty procedure, a bypass surgery, or similar procedure to reduce or remove the restenosis. In recent years, various devices and methods (other than bypass surgery) for the prevention of restenosis after arterial intervention in a patient's body lumen have become known which typically use an expandable graft (commonly termed "stent") on the distal end of the catheter designed for implantation in the body lumen.
Stents generally are designed for permanent implantation within the body lumen. By way of example, several stent devices and methods can be found in commonly assigned and commonly owned U.S. Pat. No. 5,158,548 (Lau et al.); U.S. Pat. No. 5,242,399 (Lau et al.); U.S. Pat. No. 5,344,426 (Lau et al.); U.S. Pat. No. 5,514,154 (Lauetal.); U.S. Pat. No. 5,360,401 (Turnlandetal.); and U.S. Ser. No. 08/454,599 (Lam), which are incorporated in their entirety herein.
In recent years in practicing angioplasty, it is often desirable to exchange one dilatation catheter for another. In doing so, it is necessary to use extension wires or long exchange wires having a total length of approximately 200 to 300 centimeters, both of which typically require two operators. During the procedure, it is necessary that the operators communicate with each other to coordinate their efforts, which makes the procedure more involved and time consuming.
In addition, because the extension wires or exchange wires are long, they are awkward to handle. For that reason, they may come in contact with the floor or otherwise extend out of the sterile surgical field and become contaminated. If contaminated, the entire apparatus being utilized for the angioplasty procedure must be removed from the patient and replaced.
There have been improvements in the field of rapid exchange catheters to rectify some of the shortcomings. For example, U.S. Pat. No. 4,748,982 to Horzewski et al. discloses a method and apparatus relating to a rapid exchange balloon dilatation catheter with slitted exchange sleeve. The sleeve has a slit extending longitudinally from the proximal extremity of the sleeve to a region adjacent the balloon to permit the guide wire, which is used to assist guiding the catheter in to a vessel of a patient, to be removed therethrough. U.S. Pat. No. 5,040,548 to Yock discloses methods for performing angioplasty procedures within a patient's coronary artery to facilitate rapid exchanges of angioplasty devices. U.S. Pat. No. 5,180,368 to Garrison discloses a rapidly exchangeable and expandable cage catheter for repairing damaged blood vessels. Garrison discloses an intravascular catheter having an expandable cage mounted on the distal end of a tubular member that is radially expanded and contracted by means of a control wire. The device includes a flexible tubular element extending through the expandable cage interior to facilitate the rapid exchange of the catheter. U.S. Pat. No. 5,061,273 to Yock discloses another angioplasty apparatus facilitating rapid exchanges.
During rapid exchange catheter procedures known in the art, it is necessary for the surgeon to introduce the balloon dilitation catheter onto the guide wire already positioned within the body lumen by a backloading technique. Specifically, the guide wire remains stationary in the patient's vasculature while the distal extremity of the catheter is advanced over the guide wire proximal end. The guide wire proximal end exits through an opening on the outer surface of the catheter proximal to the balloon. However, threading the guide wire through this opening on the outer surface of the catheter is difficult and requires time and precision, especially when the catheter is covered by a protective sheath.
In addition, recent developments in stent delivery systems require use of a protective sheath to cover the stent during the delivery process, which sheath is retracted so the stent can be deployed. Use of such a sheath complicates the backloading of the guide wire during the rapid exchange catheter procedure because the guide wire must not only pass through the outer surface opening in the catheter, but it must also pass through a similar opening in the sheath. If the two openings are misaligned, backloading the guide wire becomes even more difficult.
Accordingly, there is a need for a rapid exchange catheter having a design that facilitates easy front loading and backloading of the catheter so that the guide wire passes through the catheter and sheath quickly and precisely without numerous attempts by the surgeon to align catheter and sheath openings to thread the guide wire therethrough.